Author platform or sometimes writer platform is the concept of having the ability to sell books (or other goods) because of who you are or who you can reach and very often begins with having a personal website and personal-domain as a hub.
In the pre-web era, the (centralized) publishing industry considered an author's platform their ability to reach and sell books to a broader audience. This typically applied to non-fiction authors, personalities, and celebrities that had the ability to drive a big part of the publicity for their books by appearing on/in television (talk shows, variety shows, political shows, etc.), radio, newspapers, magazines and other media (typically due to their fame). This free/less-expensive publicity was used to increase sales of books and improve margins.
In the internet era, many build their platform over a career by using a website as a primary hub where they can conglomerate followers / subscribers and engage them on a regular basis by sending them messages, updates, newsletters, and sales pitches.
IndieWeb principles and concepts like POSSE and backfeed can assist writers (and many others) by allowing them to publish in one central place and syndicate to social silos for increased reach and interaction in a DRY (don't repeat yourself) manner thus freeing up time for them to write on their projects and spend less time on outreach and publicity.
Jeremy Keith uses his website in part as an author platform to promote his books (and Clearleft, his business) by regularly writing about web design and other related topics. He also uses related personal-domains to distribute books he's written (example: https://resilientwebdesign.com/)
- Add yourself here… (see this for more details)
Many authors rely on siloed versions of social media to build their networks. This can often be a mistake because of the frequency of site-deaths or the tying of one's personal brand to that of a social silo that doesn't hold the same values as the person in question. (See also: identity)
- A Definition of Author Platform by Jane Friedman
- What is a Writer/Author Platform? on Writer's Digest